Method for performing self-interference cancellation by communication device of distributed antenna structure

ABSTRACT

A method for performing self-interference cancellation by a terminal may comprise the steps of: receiving RS configuration information for phase estimation of self-interference from a base station; when the terminal operates, with a distributed antenna structure, in a full duplex radio (FDR) mode or operates in a space division duplex (SDD) mode between panels, transmitting an RS on the basis of the RS configuration information; and performing phase estimation for self-interference between the panels on the basis of the RS. The terminal is capable of communicating with at least one of another terminal, a terminal related to an autonomous driving vehicle, a base station or a network.

TECHNICAL FIELD

The present disclosure relates to wireless communication, and moreparticularly, to a method of performing self-interference cancellationin a communication device of a distributed antenna structure.

BACKGROUND ART

Compared to conventional half duplex communication in which time orfrequency resources are divided orthogonally, full duplex communicationdoubles a system capacity in theory by allowing a node to performtransmission and reception simultaneously.

FIG. 1 is a conceptual view of a UE and a Base Station (BS) that supportFull Duplex Radio (FDR).

In the FDR situation illustrated in FIG. 1, the following three types ofinterference are produced.

Intra-device self-interference: Because transmission and reception takeplace in the same time and frequency resources, a desired signal and asignal transmitted from a BS or UE are received at the same time at theBS or UE. The transmitted signal is received with almost no attenuationat a Reception (Rx) antenna of the BS or UE, and thus with much largerpower than the desired signal. As a result, the transmitted signalserves as interference.

UE to UE inter-link interference: An Uplink (UL) signal transmitted by aUE is received at an adjacent UE and thus serves as interference.

BS to BS inter-link interference: The BS to BS inter-link interferencerefers to interference caused by signals that are transmitted betweenBSs or heterogeneous BSs (pico, femto, and relay) in a HetNet state andreceived by an Rx antenna of another BS.

Among such three types of interference, intra-device self-interference(hereinafter, self-interference (SI)) is generated only in an FDR systemto significantly deteriorate performance of the FDR system. Therefore,first of all, intra-device SI needs to be cancelled in order to operatethe FDR system.

DISCLOSURE Technical Task

One technical task of the present disclosure is to provide a method ofperforming self-interference cancellation in a user equipment of adistributed antenna structure.

Another technical task of the present disclosure is to provide a userequipment of a distributed antenna arrangement for performingself-interference cancellation.

The technical objects that can be achieved through the presentdisclosure are not limited to what has been particularly describedhereinabove and other technical objects not described herein will bemore clearly understood by persons skilled in the art from the followingdetailed description.

Technical Solutions

In one technical aspect of the present disclosure, provided herein is amethod of performing self-interference cancellation in a user equipment,the method including receiving Reference Signal (RS) configurationinformation for phase estimation of self-interference from a basestation, transmitting an RS based on the RS configuration informationwhen the user equipment operates in an inter-panel Space Division Duplex(SDD) mode or an inter-panel Full Duplex Radio (FDR) mode with adistributed antenna structure, and performing phase estimation oninter-panel self-interference based on the RS.

If the user equipment operates in the inter-panel SDD or FDR mode withthe distributed antenna structure and a scheduled MCS level of the userequipment is smaller than an MCS level threshold related to the RS or ascheduled bandwidth is smaller than a predefined bandwidth, the RS forthe phase estimation on the inter-panel self-interference may betransmitted.

The method may include transmitting to the base station a request forthe RS transmission of the user equipment for the phase estimation onthe inter-panel self-interference and receiving control informationindicating that the RS configuration information is valid from the basestation, and the RS may be transmitted based on the RS configurationinformation and the control information.

The control information may further include information on a time orfrequency location at which the RS configuration information is valid.The control information may be received via a Physical Downlink ControlChannel (PDCCH) or a Physical Downlink Shared CHannel (PDSCH).

The performing the phase estimation may further include calculating atleast one of a phase noise or a phase coefficient.

The phase noise may be calculated based on a phase change betweenadjacent time regions in which the RS is transmitted and the phasecoefficient may be calculated based on a phase change between adjacentfrequency regions in which the RS is transmitted.

The method may further include performing the self-interferencecancellation based on the phase estimation. The self-interferencecancellation may be performed in a baseband stage of the user equipment,and the self-interference cancellation may correspond to digitalself-interference cancellation.

The RS configuration information may be received through RRC signaling.

The RS may include one of a DeModulation RS (DMRS), a Sounding ReferenceSignal (SRS), and a Phase Tracking-Reference Signal (PT-RS). The userequipment may conceptually include a vehicle.

In another technical aspect of the present disclosure, provided hereinis a user equipment for performing self-interference cancellation, theuser equipment including a receiver configured to receive ReferenceSignal (RS) configuration information for phase estimation onself-interference from a base station, a transmitter configured totransmit an RS based on the RS configuration information when the userequipment operates in an inter-panel Space Division Duplex (SDD) or FullDuplex Radio (FDR) mode with a distributed antenna structure, and aprocessor configured to perform phase estimation on inter-panelself-interference based on the RS.

If the user equipment operates in the inter-panel SDD or FDR mode withthe distributed antenna structure and a scheduled MCS level of the userequipment is smaller than an MCS level threshold related to the RS or ascheduled bandwidth is smaller than a predefined bandwidth, thetransmitter may be controlled to transmit the RS for the phaseestimation on the inter-panel self-interference.

The transmitter may be configured to transmit a request message fortransmitting the RS to the base station, the receiver may be configuredto receive control information indicating that the RS configurationinformation is valid from the base station, and the transmitter may beconfigured to transmit the RS based on the RS configuration informationand the control information.

Advantageous Effects

According to one embodiment of the present disclosure, by using thesignaling of the present disclosure for performing self-interferencecancellation utilizing an idle transmission module of a panel operatingin a reception mode in a user equipment (including a vehicle) of adistributed antenna structure, self-interference cancellation can beperformed more efficiently.

Effects obtainable from the present disclosure may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present disclosure pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure, illustrate embodiments of thedisclosure and together with the description serve to explain theprinciple of the disclosure.

FIG. 1 is a diagram illustrating a network supporting afull-duplex/half-duplex communication operation scheme of a UE, which isproposed in the present disclosure.

FIG. 2 is a block diagram of configurations of a base station 105 and auser equipment 110 in a wireless communication system 100.

FIG. 3 is a diagram illustrating the concept of a transmission/receptionlink and self-interference (SI) in an FDR communication situation.

FIG. 4 is a diagram illustrating positions at which three Self-ICschemes are applied, in an RF Tx and Rx end (or an RF front end) of adevice.

FIG. 5 is a block diagram of a Self-IC device in a proposedcommunication apparatus in an OFDM communication environment based onFIG. 4.

FIG. 6 is a diagram illustrating application of a spatial divisioncommunication (SDD) in a vehicle to which distributed antennas areapplied.

FIG. 7 is a diagram illustrating a comparison example of a case that SDDis not applied and a case that SDD is applied.

FIG. 8 is a diagram illustrating an example of an RF front-end structureof a communication device for analog self-interference cancellation.

FIG. 9 is a diagram illustrating an example that RF self-interferencecancellation is performed using a true time delay when two distributedantenna panels exist.

FIG. 10 is a diagram illustrating three components and effects in RFself-interference cancellation (SIC).

FIG. 11 is a diagram illustrating an example that RF SIC is performedusing phase compensation in a baseband when two distributed antennapanels exist.

FIG. 12 is a diagram illustrating an example that RF SIC is performedusing phase compensation in a baseband and a digital delay device whentwo distributed antenna panels exist.

FIG. 13 is a diagram illustrating an example of inter-panel interferencein which analog beamforming is considered.

BEST MODE FOR DISCLOSURE

Reference will now be made in detail to the preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. In the following detailed description of thedisclosure includes details to help the full understanding of thepresent disclosure. Yet, it is apparent to those skilled in the art thatthe present disclosure can be implemented without these details. Forinstance, although the following descriptions are made in detail on theassumption that a mobile communication system includes 3GPP LTE system,the following descriptions are applicable to other random mobilecommunication systems in a manner of excluding unique features of the3GPP LTE.

Occasionally, to prevent the present disclosure from getting vaguer,structures and/or devices known to the public are skipped or can berepresented as block diagrams centering on the core functions of thestructures and/or devices. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Besides, in the following description, assume that a terminal is acommon name of such a mobile or fixed user stage device as a userequipment (UE), a mobile station (MS), an advanced mobile station (AMS)and the like. And, assume that a base station (BS) is a common name ofsuch a random node of a network stage communicating with a terminal as aNode B (NB), an eNode B (eNB), an access point (AP) and the like.Although the present specification is described based on IEEE 802.16msystem, contents of the present disclosure may be applicable to variouskinds of other communication systems.

In a mobile communication system, a user equipment is able to receiveinformation in downlink and is able to transmit information in uplink aswell. Information transmitted or received by the user equipment node mayinclude various kinds of data and control information. In accordancewith types and usages of the information transmitted or received by theuser equipment, various physical channels may exist.

The following descriptions are usable for various wireless accesssystems including CDMA (code division multiple access), FDMA (frequencydivision multiple access), TDMA (time division multiple access), OFDMA(orthogonal frequency division multiple access), SC-FDMA (single carrierfrequency division multiple access) and the like. CDMA can beimplemented by such a radio technology as UTRA (universal terrestrialradio access), CDMA 2000 and the like. TDMA can be implemented with sucha radio technology as GSM/GPRS/EDGE (Global System for Mobilecommunications)/General Packet Radio Service/Enhanced Data Rates for GSMEvolution). OFDMA can be implemented with such a radio technology asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, E-UTRA (EvolvedUTRA), etc. UTRA is a part of UMTS (Universal Mobile TelecommunicationsSystem). 3GPP (3rd Generation Partnership Project) LTE (long termevolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA. The 3GPPLTE employs OFDMA in DL and SC-FDMA in UL. And, LTE-A (LTE-Advanced) isan evolved version of 3GPP LTE.

Moreover, in the following description, specific terminologies areprovided to help the understanding of the present disclosure. And, theuse of the specific terminology can be modified into another form withinthe scope of the technical idea of the present disclosure.

FIG. 2 is a block diagram for configurations of a base station 105 and auser equipment 110 in a wireless communication system 100.

Although one base station 105 and one user equipment 110 (D2D userequipment included) are shown in the drawing to schematically representa wireless communication system 100, the wireless communication system100 may include at least one base station and/or at least one userequipment.

Referring to FIG. 2, a base station 105 may include a transmitted (Tx)data processor 115, a symbol modulator 120, a transmitter 125, atransceiving antenna 130, a processor 180, a memory 185, a receiver 190,a symbol demodulator 195 and a received data processor 197. And, a userequipment 110 may include a transmitted (Tx) data processor 165, asymbol modulator 170, a transmitter 175, a transceiving antenna 135, aprocessor 155, a memory 160, a receiver 140, a symbol demodulator 155and a received data processor 150. Although the base station/userequipment 105/110 includes one antenna 130/135 in the drawing, each ofthe base station 105 and the user equipment 110 includes a plurality ofantennas. Therefore, each of the base station 105 and the user equipment110 of the present disclosure supports an MIMO (multiple input multipleoutput) system. And, the base station 105 according to the presentdisclosure may support both SU-MIMO (single user-MIMO) and MU-MIMO(multi user-MIMO) systems.

In downlink, the transmitted data processor 115 receives traffic data,codes the received traffic data by formatting the received traffic data,interleaves the coded traffic data, modulates (or symbol maps) theinterleaved data, and then provides modulated symbols (data symbols).The symbol modulator 120 provides a stream of symbols by receiving andprocessing the data symbols and pilot symbols.

The symbol modulator 120 multiplexes the data and pilot symbols togetherand then transmits the multiplexed symbols to the transmitter 125. Indoing so, each of the transmitted symbols may include the data symbol,the pilot symbol or a signal value of zero. In each symbol duration,pilot symbols may be contiguously transmitted. In doing so, the pilotsymbols may include symbols of frequency division multiplexing (FDM),orthogonal frequency division multiplexing (OFDM), or code divisionmultiplexing (CDM).

The transmitter 125 receives the stream of the symbols, converts thereceived stream to at least one or more analog signals, additionallyadjusts the analog signals (e.g., amplification, filtering, frequencyupconverting), and then generates a downlink signal suitable for atransmission on a radio channel. Subsequently, the downlink signal istransmitted to the user equipment via the antenna 130.

In the configuration of the user equipment 110, the receiving antenna135 receives the downlink signal from the base station and then providesthe received signal to the receiver 140. The receiver 140 adjusts thereceived signal (e.g., filtering, amplification and frequencydownconverting), digitizes the adjusted signal, and then obtainssamples. The symbol demodulator 145 demodulates the received pilotsymbols and then provides them to the processor 155 for channelestimation.

The symbol demodulator 145 receives a frequency response estimated valuefor downlink from the processor 155, performs data demodulation on thereceived data symbols, obtains data symbol estimated values (i.e.,estimated values of the transmitted data symbols), and then provides thedata symbols estimated values to the received (Rx) data processor 150.The received data processor 150 reconstructs the transmitted trafficdata by performing demodulation (i.e., symbol demapping, deinterleavingand decoding) on the data symbol estimated values.

The processing by the symbol demodulator 145 and the processing by thereceived data processor 150 are complementary to the processing by thesymbol modulator 120 and the processing by the transmitted dataprocessor 115 in the base station 105, respectively.

In the user equipment 110 in uplink, the transmitted data processor 165processes the traffic data and then provides data symbols. The symbolmodulator 170 receives the data symbols, multiplexes the received datasymbols, performs modulation on the multiplexed symbols, and thenprovides a stream of the symbols to the transmitter 175. The transmitter175 receives the stream of the symbols, processes the received stream,and generates an uplink signal. This uplink signal is then transmittedto the base station 105 via the antenna 135.

In the base station 105, the uplink signal is received from the userequipment 110 via the antenna 130. The receiver 190 processes thereceived uplink signal and then obtains samples. Subsequently, thesymbol demodulator 195 processes the samples and then provides pilotsymbols received in uplink and a data symbol estimated value. Thereceived data processor 197 processes the data symbol estimated valueand then reconstructs the traffic data transmitted from the userequipment 110.

The processor 155/180 of the user equipment/base station 110/105 directsoperations (e.g., control, adjustment, management, etc.) of the userequipment/base station 110/105. The processor 155/180 may be connectedto the memory unit 160/185 configured to store program codes and data.The memory 160/185 is connected to the processor 155/180 to storeoperating systems, applications and general files.

The processor 155/180 may be called one of a controller, amicrocontroller, a microprocessor, a microcomputer and the like. And,the processor 155/180 may be implemented using hardware, firmware,software and/or any combinations thereof. In the implementation byhardware, the processor 155/180 may be provided with such a deviceconfigured to implement the present disclosure as ASICs (applicationspecific integrated circuits), DSPs (digital signal processors), DSPDs(digital signal processing devices), PLDs (programmable logic devices),FPGAs (field programmable gate arrays), and the like.

Meanwhile, in case of implementing the embodiments of the presentdisclosure using firmware or software, the firmware or software may beconfigured to include modules, procedures, and/or functions forperforming the above-explained functions or operations of the presentdisclosure. And, the firmware or software configured to implement thepresent disclosure is loaded in the processor 155/180 or saved in thememory 160/185 to be driven by the processor 155/180.

Layers of a radio protocol between a user equipment/base station and awireless communication system (network) may be classified into 1st layerL1, 2nd layer L2 and 3rd layer L3 based on 3 lower layers of OSI (opensystem interconnection) model well known to communication systems. Aphysical layer belongs to the 1st layer and provides an informationtransfer service via a physical channel. RRC (radio resource control)layer belongs to the 3rd layer and provides control radio resourcedbetween UE and network. A user equipment and a base station may be ableto exchange RRC messages with each other through a wirelesscommunication network and RRC layers.

In the present specification, although the processor 155/180 of the userequipment/base station performs an operation of processing signals anddata except a function for the user equipment/base station 110/105 toreceive or transmit a signal, for clarity, the processors 155 and 180will not be mentioned in the following description specifically. In thefollowing description, the processor 155/180 can be regarded asperforming a series of operations such as a data processing and the likeexcept a function of receiving or transmitting a signal without beingspecially mentioned.

FIG. 3 is a diagram showing the concept of a transmission/reception linkand self-interference (SI) in an FDR communication situation.

As shown in FIG. 3, SI may be divided into direct interference causedwhen a signal transmitted from a transmit antenna directly enters areceive antenna without path attenuation, and reflected interferencereflected by peripheral topology, and the level thereof is dramaticallygreater than a desired signal due to a physical distance difference. Dueto the dramatically large interference intensity, efficient self-IC isnecessary to operate the FDR system.

To effectively operate the FDR system, self-IC requirements with respectto the maximum transmit power of devices (in the case where FDR isapplied to a mobile communication system (BW=20 MHz)) may be determinedas illustrated in Table 1 below.

TABLE 1 Max. Thermal Receiver Tx Noise. Thermal Self-IC Power (BW =Receiver Noise Target Node Type (PA) 20 MHz) NF Level (PA-TN-NF) MacroeNB 46 dBm −101 dBm 5 dB −96 dBm 142 dB Pico eNB 30 dBm (for eNB) 126 dBFemto 23 dBm 119 dB eNB, WLAN AP UE 23 dBm 9 dB −92 dBm 115 dB (for UE)

Referring to Table 1, it may be noted that to effectively operate theFDR system in a 20-MHz BW, a UE needs 119-dBm Self-IC performance. Athermal noise value may be changed as N_(0,BW)=−174 dBM+10×log₁₀ (BW)according to a bandwidth of a mobile communication system. In Table 1,the thermal noise value is calculated on the assumption of a 20-MHz BW.Regarding Table 1, for Receiver Noise Figure (NF), a worst case isconsidered referring to the 3GPP specification requirements. ReceiverThermal Noise Level is determined to be the sum of a thermal noise valueand a receiver NF in a specific BW.

Types of Self-IC Schemes and Methods for Applying the Self-IC Schemes

FIG. 4 is a view illustrating positions at which three Self-IC schemesare applied, in a Radio Frequency (RF) Tx and Rx end (or an RF frontend) of a device. Now, a brief description will be given of the threeSelf-IC schemes.

Antenna Self-IC: Antenna Self-IC is a Self-IC scheme that should beperformed first of all Self-IC schemes. SI is cancelled at an antennaend. Most simply, transfer of an SI signal may be blocked physically byplacing a signal-blocking object between a Tx antenna and an Rx antenna,the distance between antennas may be controlled artificially, usingmultiple antennas, or a part of an SI signal may be canceled throughphase inversion of a specific Tx signal. Further, a part of an SI signalmay be cancelled by means of multiple polarized antennas or directionalantennas.

Analog Self-IC: Interference is canceled at an analog end before an Rxsignal passes through an Analog-to-Digital Convertor (ADC). An SI signalis canceled using a duplicated analog signal. This operation may beperformed in an RF region or an Intermediate Frequency (IF) region. SIsignal cancellation may be performed in the following specific method. Aduplicate of an actually received SI signal is generated by delaying ananalog Tx signal and controlling the amplitude and phase of the delayedTx signal, and subtracted from a signal received at an Rx antenna.However, due to the analog signal-based processing, the resultingimplementation complexity and circuit characteristics may causeadditional distortion, thereby changing interference cancellationperformance significantly.

Digital Self-IC: Interference is canceled after an Rx signal passesthrough an ADC. Digital Self-IC covers all IC techniques performed in abaseband region. Most simply, a duplicate of an SI signal is generatedusing a digital Tx signal and subtracted from an Rx digital signal. Ortechniques of performing precoding/postcoding in a baseband usingmultiple antennas so that a Tx signal of a UE or an eNB may not bereceived at an Rx antenna may be classified into digital Self-IC.However, since digital Self-IC is viable only when a digital modulatedsignal is quantized to a level enough to recover information of adesired signal, there is a need for the prerequisite that the differencebetween the signal powers of a designed signal and an interferencesignal remaining after interference cancellation in one of theabove-described techniques should fall into an ADC range, to performdigital Self-IC.

FIG. 5 is a block diagram of a Self-IC device in a proposedcommunication apparatus in an OFDM communication environment based onFIG. 4.

While FIG. 5 shows that digital Self-IC is performed using digital SIinformation before Digital to Analog Conversion (DAC) and after ADC, itmay be performed using a digital SI signal after Inverse Fast FourierTransform (IFFT) and before Fast Fourier Transform (FFT). Further,although FIG. 5 is a conceptual view of Self-IC though separation of aTx antenna from an Rx antenna, if antenna Self-IC is performed using asingle antenna, the antenna may be configured in a different manner fromin FIG. 5. A functional block may be added to or removed from an RF Txend and an RF Rx end shown in FIG. 5 according to a purpose.

Hereinafter, the present disclosure is intended for self-interferencecancellation in a UE (particularly, vehicle), and more particularly,suggests a method for performing self-interference cancellation by usingan idle transmission module of a panel operating in a reception mode ina distributed antenna structure.

Space division duplex considered in the present disclosure is a schemefor independently managing a communication link of each antenna byperforming space division for each antenna. In order to independentlymanage a communication link per antenna, self-interference betweenantennas owned by a UE should be removed, and interference between UEsincluded in a communication link should be reduced.

As a scheme for removing self-interference between antennas owned by aUE, there is an analog and digital self-interference cancellation schemeor a scheme for reducing self-interference by making sure of a distancebetween antennas. Since the scheme for reducing self-interference bymaking sure of a distance between antennas has lower complexity thanthat of the analog and digital self-interference cancellation scheme,the scheme for reducing self-interference by masking sure of a distancebetween antennas is easily applicable to the system. The scheme forreducing self-interference by masking sure of a distance betweenantennas may be applied by making sure of a distance between antennas ina vehicle UE larger than the existing communication UE. An inter-cellinterference reduction scheme of the existing cellular communicationsystem may be applied to the scheme for reducing interference betweenUEs. In current cellular communication at a high frequency band of 6 GHzor more, since a narrow beam width is formed for a communicationdistance, it is considered that the probability of interference due tooverlapped beams of neighboring cells is low. Also, it is likely that asignal may be blocked by an object due to linearity of the signal. Sincea vehicle has a surface made of iron and a big size, the vehicle islikely to block a high frequency signal of a neighboring UE.

Space division communication is easily applicable to high frequencycommunication between vehicles having distributed antennas due to theabove characteristics. If space division communication is applied, sincelinks of antennas are isolated from one another, transmission andreception timing points of the respective communication links may beallocated differently and frequency resources may be reused in eachcommunication link.

FIG. 6 is a diagram illustrating application of a spatial divisioncommunication (SDD) in a vehicle to which distributed antennas areapplied.

In FIG. 6, a link 1 and a link 2 are communication links connected withdifferent devices (UE or base station). The amount of Tx resources andRx resources may be changed depending on a status of each communicationlink, and Tx timing point and Rx timing point may also be changed. Aradio unit (RU) shown in FIG. 6 is an antenna module that includes aplurality of antennas. In this case, a UE includes four RUs that aredistributed. Two of four RUs are used to form the link 1, and the othertwo RUs are used to form the link 2.

In the case that SDD is applied to a plurality of UEs, it isadvantageous that transmission may be performed using more resources formore several times within a target time than the case that SDD is notapplied to a plurality of UEs. FIG. 7 illustrates a comparison exampleof a case that SDD is not applied and a case that SDD is applied.

Referring to FIG. 7, a left drawing illustrates communication betweenvehicles to which SDD is not applied, and a right drawing illustratescommunication between vehicles to which SDD is applied. In the case thatSDD is not applied, the UE transmits a signal to different UEs inaccordance with a multiplexing mode at the same time. If three UEsintend to form a communication link with their neighboring UE as shownin FIG. 7, each UE should be allocated with one transmission resourceand two reception resources. If SDD is applied, the UE has only to formone transmission resource and one reception resource per communicationlink, the UE may perform signal transmission within a unit time for moretimes than the case that SDD is not applied. If SDD is applied,frequency resources are divisionally allocated to neighboring UEs thattransmit signals simultaneously with the corresponding UE. If SDD isapplied, since transmission signals of the respective UEs are spatiallydivided, the same frequency resource may be used, whereby frequencyresources used by each communication link are increased.

In addition to the aforementioned advantages, since a reception UE ofeach communication link receives a signal by using narrow receptionbeams for space division, it is not likely that the UE is affected byjamming. In addition, since a neighboring vehicle is likely to block thesignal, it is difficult to perform jamming at a long distance. Asadditional advantage, since a base station does not need to manageresources between communication groups to be orthogonal to resources inthe communication groups, complexity in resource management of the basestation is reduced.

In 3GPP TR 22.886, a scenario where 15840 vehicles exist per 1 mile isincluded. In this case, in order that a base station respectivelymanages communication links between respective vehicles, complexity ofthe base station is too increased. However, if SDD is applied, UEsincluded in the communication links have only to determine atransmission timing point and a reception timing point, complexity ofthe base station is reduced.

FIG. 8 is a diagram illustrating an example of an RF front-end structureof a communication device for analog self-interference cancellation.

A basic principle in an analog domain is that a partial power of atransmission signal is diverged and then deformed to make a duplicatesignal of a self-interference signal, which is actually received, anddeduct the duplicate signal from a signal received in a receptionantenna. In this case, several combinations of a true time delay, aphase shifter and an attenuator may be used to make a signal similar tothe received self-interference signal from the diverged transmissionsignal.

However, it is physically difficult to transmit a signal to transmissionpanels, which are far away from each other, by diverging the signal fromthe transmission panels while minimizing distortion when SDD betweenpanels is configured in a vehicle (operating in FDR mode) based ondistributed antennas. When RF signal is transmitted between panels thatare physically far away from each other, time delay due to transmissionand signal attenuation occur, whereby it is apparent that signaldistortion occurs. Therefore, when SDD between panels or FDR in a panelis configured in a vehicle based on distributed antennas, an approachdifferent from a self-interference cancellation scheme of an analogdomain in the existing UE or base station is required.

The present disclosure proposes a method of performing inter-panelself-interference cancellation using an idle transmission and receptionRF chain existing in a corresponding panel when a specific paneloperates in a reception mode in the structure of a distributed antenna.The transmission and reception RF chains exist in a pair-wise mannerinside the panel of the distributed antenna. An RF chain of thetransmission RF chain or the reception RF chain is selected by using aswitch, and then connected to the antenna by the switch. When a specificpanel operates in transmission/reception mode, there is an idlereception/transmission RF chain, which is not used, in the correspondingpanel. The received inter-panel interference is diverged by activatingthe idle reception/transmission RF chain so as to come within thedynamic range of the ADC (in the case of using the reception RF chain),or it is possible to perform inter-panel self-interference cancellationin the analog domain by creating an RF signal capable of modelinginter-panel interference (in the case of using the transmission RFchain). The present disclosure is written by targeting a case ofutilizing the transmission RF chain.

Suggestion 1

RF signal may be generated using an idle transmission RF chain of areception panel from a signal transmitted from a baseband unit, andself-interference cancellation between distributed panels may beperformed in an analog domain. If the idle transmission RF chain isused, RF signal for self-interference cancellation may be made even inan environment of distributed antennas. For convenience of description,it is assumed that two distributed units exist as described in theembodiment of FIG. 9.

FIG. 9 is a diagram illustrating an example that RF self-interferencecancellation is performed using a true time delay when two distributedantenna panels exist.

In FIG. 9, it may be assumed that a baseband unit is located inside avehicle and distributed radio units (RUs) exist in several positions ofthe vehicle. For concept of SDD, it may be assumed that a distributedradio unit 1 (RU 1) is set to Tx mode and a distributed radio unit 2 (RU2) is set to Rx mode. Cancellation of self-interference generated fromthe distributed RU 1 is required by the distributed RU 2. To this end,the idle transmission RF chain of the distributed RU 2 receives abaseband signal in the distributed RU 1 and then passes through severalblocks of Tx chain like the distributed RU 1. Afterwards, thedistributed RU 2 may naturally make a signal similar to the RF signalgenerated from the distributed RU.

A phase shifter and an attenuator already exist for analog beamforming(BF) in each antenna of the distributed RU. Therefore, two of threecomponents required for analog self-interference cancellation alreadyexist, and the distributed RU adds time delay between Tx chain and Rxchain to an analog self-interference cancellation circuit. Various typesof adaptive algorithms may be used for a mechanism for controlling eachof the phase shifter and the attenuator of analog self-interferencecancellation.

FIG. 10 is a diagram illustrating three components and effects in RFself-interference cancellation (SIC).

In FIG. 10, three components in RF SIC illustrate a self-interferencecancellation effect. The attenuator vertically moves a magnitude of asignal, and the phase shifter vertically moves a phase of a signal.Finally, the true time delay varies a slope in a phase of a signal.

In the suggestion 1, a circuit of the true time delay is included in anmmWave band. However, it is difficult to make a true time delay normallyoperating in an mmWave band, and the true time delay is not a commercialdevice and therefore its cost may be expensive. Therefore, the followingsuggestion 2 intends to suggest a method for implementing an effect of aphase change, which occurs after passing through a true time delay, in abaseband.

Suggestion 2

A specific phase value per tone of transmission data transmitted from abaseband is previously compensated based on a channel estimation valueof interference between patterns, an effect such as a phase changeoccurring after passing through the true time delay may be obtained whena self-interference signal is generated. RF signal may be generatedusing an idle transmission RF chain of a reception panel, andself-interference cancellation between distributed panels may beperformed in an analog domain.

FIG. 11 is a diagram illustrating an example that RF SIC is performedusing phase compensation in a baseband when two distributed antennapanels exist.

Since an idle transmission chain of a panel defined by Rx is used, asignal may be obtained from RF of the existing Tx chain and deformationfor self-interference cancellation from the baseband may be performedwithout signal deformation.

Referring to FIG. 11, a communication device may include a baseband unit1110, a first distributed RU 1120, and a second distributed RU 1130. Thebaseband unit 1110 may include a first transmission chain 1140 and asecond transmission chain 1150. A processor may estimate a phase change,which occurs after passing through a time delay, through a pilot, and asshown in FIG. 11, a phase compensator 1160 in the baseband unit maypreviously compensate for the estimated phase coefficient value per tonewith respect to a digital signal of a baseband, and may multiply a phasevalue, which is previously estimated and calculated, by each tone ofdata transmitted to obtain a phase distortion effect the same as thephase change occurring after passing through the time delay. Acorresponding equation is as follows.

Y(s)=e ^(jθ) ^(s) *X(s), where s=1 . . . N  [Equation 1]

That is, each tone may be multiplied by e^(jθ) ^(s) which is apreviously calculated phase value, whereby an effect of the above truetime delay may be obtained. In more detail, e^(jθ) ^(s) may becalculated by the following procedures:

1. e^(jθ) ^(s1) : phase value per tone calculated by a fixed delay froman idle Tx chain to a coupler;

2. e^(jθ) ^(s2) : phase value per tone calculated by a group delay ofmeasured self-interference; and

3. e^(jθ) ^(s) =e^(jθ) ^(s22) −e^(jθ) ^(s1)

As described above, since e^(jθ) ^(s1) which is a fixed delay of adevice is previously calibrated and calculated, if e^(jθ) ^(s2) isobtained, e^(jθ) ^(s) may be calculated automatically. If is previouslycompensated by the baseband to generate a self-interference signal, thesame effect as the true time delay may be obtained in the same manner asthe suggestion 1, and a self-interference cancellation unit 1170 of thesecond distributed RU 1130 in the RF domain may cancelself-interference. The signal phase-compensated through the phasecompensator 1160 is connected to the second Tx chain 1150, and isdelivered from the second Tx chain 1150 to the second distributed RU1130.

The self-interference cancellation unit 1170 may be a type of a coupler,and may cancel self-interference in such a way of deducting the signaldelivered from the second Tx chain 1150 to the second distributed RU1130 from the self-interference signal received by the seconddistributed RU 1130 through the phase compensated (or corrected) signal.

Suggestion 2-1

A phase offset value of each tone may be estimated and compensated byinterpolation based on phase information of a complex value of a pilotthat is previously defined.

The phase offset value to be compensated should be estimated for alltones. However, since it is almost impossible to estimate the phaseoffset value in commercial use due to high overhead, a phase valuecorresponding to the other tones should be estimated by a phase valueestimated by a specific pilot. To this end, pilots (or tones andreference signals) for phase offset may be arranged uniformly, and theother values may be estimated by various methods (for example, linearinterpolation method or various types of interpolation methods) tocompensate for coefficient values of all tones.

Suggestion 3

In order to compensate for phase in a baseband and obtain a physicaldelay effect in a true time delay, a self-interference signal may begenerated using a digital delay device, RF signal may be generated usingan idle Tx RF chain of a reception panel, and self-interferencecancellation between distributed panels may be performed in an analogdomain.

FIG. 12 is a diagram illustrating an example that RF SIC is performedusing phase compensation in a baseband and a digital delay device whentwo distributed antenna panels exist.

Even though a phase of a baseband signal has been compensated to bematched with estimated phase values of self-interference, timesynchronization may not be actually matched by a physical time delay. Incase of OFDM signal, if an error of time synchronization occurs within acyclic prefix (CP), signal recovery is sufficiently possible even in anenvironment where a synchronization error is not compensated. However,if a self-interference signal is made beyond the CP, inter-symbolinterference (ISI) is generated. To solve this, the time when the signalis made may physically be delayed using a digital delay device. Thisallows the signal to be recovered and removed within the CP. Thesuggestion 3 may be used together with the suggestion 2.

The suggestions described as above may selectively operate only when aBS or UE operates in FDR mode. The BS may operate in the FDR mode in thefollowing cases: a UE operating in the FDR mode accesses the BS or a UEthat desires downlink reception and a UE that desires uplinktransmission desire to perform communication at the same time. In thiscase, the method may selectively operate. Generally, since downlinktraffic is greater than uplink traffic, some of UEs that desire uplinktransmission may operate in the FDR mode in order for a certain UE tooperate in the FDR mode. In this case, the corresponding method mayselectively operate.

For example, the BS may predict a duration of UE's FDR operation basedon a buffer status report (BSR) and trigger UE's control signaltransmission so as to receive necessary information from the UE througha physical layer signal or higher layer signal at a desired time.

Examples of the above-described suggested method may be considered asone method for implementing the present disclosure. Also, although theabove-described suggested methods may be implemented independently, someof the above-described suggested methods may be implemented in the formof combination (or merge). A rule may be defined such that informationon whether the suggested methods are applied (or information on rulesrelated to the suggested methods) should be transmitted from a BS to aUE through a predefined signal (e.g., physical layer signal, higherlayer signal, etc.).

Hereinafter, for self-interference cancellation using an RF in a userequipment (including a vehicle), a signaling method related to phaseestimation necessary for performing self-interference cancellation byutilizing an idle transmission module of a panel operating in areception mode in a distributed antenna structure will be described.

FIG. 13 is a diagram illustrating an example of inter-panel interferencein which analog beamforming is considered.

This example relates to a case in which interference occurs between atransmission panel and a reception panel in the same vehicle whenvehicle-to-vehicle communication is performed using a distributedantenna in a vehicle. Analog beamforming may be applied to each panel,and it may be observed that inter-panel interference occurs according toan analog beamforming index.

As shown in FIG. 13, a right front A-filler side panel of a vehicle isdefined as Tx and five analog Tx beams (indexes #0, #1, #2, #3, and #4)exist on this panel. A left front A-filler side panel is defined as Rxand there are 5 analog Rx beams (indexes #0, #1, #2, #3, and #4) on thispanel. In such a case, total 25 pairs of inter-panel interferences bythe beam indexes of each panel may be generated as follows.

(Tx beam index, Rx beam index)={(#0,#0), (#0,#1), (#0,#2),(#0,#3)(#0,#4), (#1,#0), (#1,#1), (#1,#2), (#1,#3)(#1,#4), (#2,#0),(#2,#1), (#2,#2), (#2,#3)(#2,#4),(#3,#0)(#3,#1)(#3,#2)(#3,#3)(#3,#4)(#4,#0)(#4,#1)(#4,#2)(#4,#3)(#4,#4)}

In FIG. 13, one transmission panel and one reception panel areillustrated as dispersedly disposed in a vehicle, but a plurality oftransmission panels and a plurality of reception panels may bedispersedly disposed. In this case, the panel and the beam may beconfigured in a manner of being paired in consideration ofself-interferences between Tx beams of each transmission panel and Rxbeams of each reception panel.

In the distributed antenna environment, an inter-panel interferencesignal generated due to the reflector may change a phase slope due to agroup delay of the signal. In order to remove it from the analog domain,it is necessary to compensate for a delay (i.e., phase slope). In theconventional sub-6 GHz, the delay is compensated for by using a truetime delay element. However, it may be difficult to manufacture a truetime delay in the mmWave band, and it may be replaced with basebandphase compensation and RF signal generation using an idle Tx chain, sothat RF Self-Interference Cancellation (SIC) can be performed in theanalog domain without the burden of additional hardware.

In order to compensate for a phase slope of an inter-panel interferencesignal in a distributed antenna environment, it is first necessary toestimate the phase slope on the baseband. That is, in order tocompensate for phase coefficient on the baseband for the SIC in an RFdomain by using a distributed antenna, it is necessary to estimate aphase slope or a phase distortion degree by a group delay. Hereinafter,a signaling method for phase estimation and compensation for phasecoefficient compensation on a baseband will be described.

AGC control must be involved to prevent ADC saturation in the RF chaindue to inter-panel interference received at large power by reflectedinterference due to interference reflecting from the reflector. That is,in estimating interference, not decoding a signal, the interferenceshould be estimated by the AGC setting according to the received powerof the interference. However, since AGC basically sets a gain value inaccordance with a large signal, special setting is not required. Sinceinterference cancellation is performed in an analog stage of acommunication device at the time of performing the interferencecancellation thereafter, if the interference cancellation is properlyperformed, the power of the reflected inter-panel interference isreduced, whereby a gain value of the AGC is also changed and comeswithin the rage of the ADC saturation.

In addition, in the distributed antenna environment, the same oscillatoris shared between the Tx RF chain and the Rx RF chain, but phase noiseoccurs due to different transmission/reception times, and thecommunication device needs to estimate the phase noise through PhaseTracking-Reference Signal (PT-RS). That is, since a phase noise value atthe time for a Tx signal to enter the RS RF chain is different from aphase noise value at the time for a signal to be generated from the TxRF chain in the communication device, phase noise is inevitably presenteven if the oscillator is shared. Such a phase noise causes performancedegradation when interference cancellation is performed.

In 5G NR, a Base Station (BS) may use RRC signaling when configuringPT-RS for a UE. In this case, the PT-RS may be in a state of beingimplicitly configured to be enabled only if a scheduled MCS level(I_(MCS)) of a UE/vehicle exceeds ptrs-MCS₁ or a scheduling bandwidth(N_(RB)) (number of RBs) exceeds N_(RB0).

Here, the N_(RB0) value is a threshold value set in advance by the BS,and this value can be overwritten through RRC in the future. The N_(RB0)value may be a predetermined number of RB thresholds for determiningwhether or not the PT-RS is enabled for a UE that does not have adistributed antenna arrangement structure. And, the ptrs-MCS1 may be aprescribed threshold value of an MCS level related to the PT-RS. Thatis, the ptrs-MCS1 may be an MCS level threshold value for determiningwhether to enable the PT-RS for the UE that does not have thedistributed antenna arrangement structure.

In case that there is SDD capability (or FDR capability) in adistributed antenna mounted vehicle, although a scheduled MCS level(IM_(CS)) of a UE/vehicle is smaller than ptrs-MCS1 or a schedulingbandwidth (N_(RB)) is smaller than N_(BRO), since it is necessary toenable PT-RS) e.g., enabled by setting a UL-PTRS-present field, which isa higher layer parameter, to ‘PN’), the vehicle may make a request forthe PT-RS to the BS and the BS may need to explicitly configure thePT-RS for the vehicle.

Alternatively, when a UE (including a vehicle) operates in FDR/SDD mode(e.g., a case that a BS simultaneously allocates resources (DL & UL, DL& Side Link (SL), UL & SL, or SL & SL to the UE), the UE makes a requestfor PT-RS configuration to the BS as desiring to operate in FDR/SDD, orthe UE is coupled with an enable field of the FDR/SDD mode of theUE/vehicle, ON/OFF operation of the PT-RS may be possible.

The following procedure is a procedure related to phase estimation,calculation and compensation. The detailed method is described asfollows.

A UE makes a request for RS resource allocation for phase estimation ofself-interference to a BS. Here, the RS for the phase estimation mayinclude DM-RS, SRS, PT-RS, etc.

DM-RS: A UE may estimate a phase value using DM-RS for transmittingdata. In addition, the UE may make a request for an additional DM-RS formore accurate phase estimation to the BS.

SRS: A UE can estimate a phase value using SRS for sounding. Inaddition, the UE can transmit a request for SRS transmission to a basestation for phase estimation at a required time.

PT-RS: A UE can use PT-RS for phase noise estimation in case of highorder modulation. However, in case of low order modulation, the UE canmake a request for PT-RS to a base station for phase noise estimation.

Signaling for RS

RS configuration information such as additional DM-RS, SRS, PT-RS or thelike for a UE to estimate a phase coefficient may be notified to the UEthrough predefined signaling (e.g., Radio Resource Control (RRC)signaling, Downlink Control Information (DCI), Physical Downlink ControlChannel (PDCCH), etc.). Here, the RS configuration information mayinclude information indicating a position of RS. For example, the RSconfiguration information may include periodicity information of RS,location or offset information of an RS located slot (or subframe),location or offset information of an RS located symbol, location oroffset information of an RS located frequency, etc.

A base station may inform a UE through predefined signaling so that theUE can be aware of the pre-defined RS configuration information. This RSconfiguration information may be configured to be cell-specific,group-specific, or UE-specific. In addition, in case of‘group-specific’, it means grouping a plurality of UEs, which may be agroup of UEs in the same serving cell or a group of UEs in differentcells. A method of grouping UEs may be based on location of UE, UE-to-UEchannel, capability of UE (e.g., FDR capable, SDD capable, etc.).

In case that a UE makes a request for transmission of DM-RS, SRS, PT-RSor the like for phase estimation in inter-panel interference to a BS,the following implicit or explicit method may be possible.

Implicit Method:

A base station transmits RS configuration information to a UE throughpredefined signaling. The UE may implicitly know that the correspondingRS configuration information (or the corresponding RS configuration) isvalid if a specific condition is satisfied. If this specific conditionis satisfied, the UE performs a phase measurement of actual inter-panelinterference. Here, the specific condition may include capabilityinformation of FDR or SDD of a vehicle or UE. In addition, the specificcondition contain information indicating that interference cancellationof an RX chain is not performed properly, which can be known throughpresence of non-presence of ADC saturation.

Explicit Method

A base station may inform a UE that RS configuration information isvalid through predefined signaling (e.g., existing DCI or new DCI), andinstruct the UE to perform a phase measurement on the RS resource. Theexisting or new DCI may additionally include time and/or frequencylocation information in which the RS configuration information is valid.That is, it means that a valid RS among a plurality of RSs can beseparately indicated. The base station may inform the UE of theinstructions on PDCCH or PDSCH.

As one embodiment, a field indicating that the RS configurationinformation is valid may be added to an existing DCI. Table 2 below is atable showing values and corresponding descriptions of an RSconfiguration information field included in DCI.

TABLE 2 RS configuration information field Description ‘0’ Allconfiguration information (or RS) for phase coefficient estimation andphase noise estimation is not valid. ‘1’ All configuration information(or RS) for phase coefficient estimation and phase noise estimation isvalid.

As another embodiment, a field indicating whether specific RSconfiguration information is valid and an RS configuration informationfield additionally indicating frequency location information coupled theformer field may be added to an existing DCI. Table 3 below is a tableshowing values and corresponding descriptions of an RS configurationinformation field included in DCI.

TABLE 3 RS configuration information field Description ‘00’ Allconfiguration information (or RS) for phase coefficient estimation andphase noise estimation is not valid. ‘01’ Configuration information (orRS) for phase coefficient estimation is valid but the rest configurationinformation (or RS) for phase noise estimation is unavailable. ‘10’Configuration information (or RS) for phase noise estimation is validbut the rest configuration information (or RS) for phase coefficientestimation is unavailable. ‘11’ All configuration information (or RS)for phase coefficient estimation and phase noise estimation is valid.

In Table 2 and Table 3, the field name added to the existing DCI isreferred to as the RS configuration information field, but it may becalled various other forms.

Phase Coefficient Calculation

In performing channel estimation, a UE may estimate a phase slope ofself-interference with a phase difference between frequency regions(e.g., subcarrier(s) or Physical Resource Blocks (PRBs)) adjacent toeach other among frequency regions (e.g., subcarrier(s) or PhysicalResource Blocks (PRBs)) on which the RS is transmitted. However, inorder to increase the accuracy of the phase slope estimation (forexample, when estimation is required a plurality of times in a slot bymobility), the UE may make a request for configuration/transmission ofadditional DM-RS to a base station.

Phase Noise Calculation

A UE may estimate (or calculate) a phase noise of self-interferencebased on a phase change between time regions (e.g., adjacent symbol (orsampling time) units) adjacent to each other among time regions (e.g.,adjacent symbol (or sampling time) units) in which the RS istransmitted.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present disclosure in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. In addition, some structural elementsand/or features may be combined with one another to constitute theembodiments of the present disclosure. The order of operations describedin the embodiments of the present disclosure may be changed. Somestructural elements or features of one embodiment may be included inanother embodiment or may be replaced with corresponding structuralelements or features of another embodiment. Moreover, it will beapparent that some claims referring to specific claims may be combinedwith other claims referring to the other claims other than the specificclaims to constitute the embodiment or add new claims by means ofamendment after the application is filed.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

A method of performing self-interference cancellation in a UE of adistributed antenna structure is industrially applicable to variouswireless communication systems such as a 5G communication system and thelike.

1. A method of performing self-interference cancellation in a user equipment, the method comprising: receiving Reference Signal (RS) configuration information for phase estimation of self-interference from a base station; transmitting an RS based on the RS configuration information based on that the user equipment operates in an inter-panel Space Division Duplex (SDD) mode or an inter-panel Full Duplex Radio (FDR) mode with a distributed antenna structure; and performing phase estimation on inter-panel self-interference based on the RS.
 2. The method of claim 1, wherein based on that the user equipment operates in the inter-panel SDD or FDR mode with the distributed antenna structure and a scheduled MCS level of the user equipment is smaller than an MCS level threshold related to the RS or a scheduled bandwidth is smaller than a predefined bandwidth, the RS for the phase estimation on the inter-panel self-interference is transmitted.
 3. The method of claim 1, further comprising: transmitting to the base station a request for the RS transmission of the user equipment for the phase estimation on the inter-panel self-interference; and receiving control information indicating that the RS configuration information is valid from the base station, wherein the RS is transmitted based on the RS configuration information and the control information.
 4. The method of claim 3, wherein the control information further comprises information on a time or frequency location at which the RS configuration information is valid.
 5. The method of claim 1, wherein the performing the phase estimation further comprises calculating at least one of a phase noise or a phase coefficient.
 6. The method of claim 5, wherein the phase noise is calculated based on a phase change between adjacent time regions in which the RS is transmitted and wherein the phase coefficient is calculated based on a phase change between adjacent frequency regions in which the RS is transmitted.
 7. The method of claim 1, further comprising performing the self-interference cancellation based on the phase estimation.
 8. The method of claim 1, wherein the self-interference cancellation is performed in a baseband stage of the user equipment.
 9. The method of claim 3, wherein the control information is received via a Physical Downlink Control Channel (PDCCH) or a Physical Downlink Shared CHannel (PD SCH).
 10. The method of claim 1, wherein the RS configuration information is received through RRC signaling.
 11. The method of claim 1, wherein the RS comprises one of a DeModulation RS (DMRS), a Sounding Reference Signal (SRS), and a Phase Tracking-Reference Signal (PT-RS).
 12. The method of claim 1, wherein the user equipment comprises a vehicle.
 13. A user equipment for performing self-interference cancellation, the user equipment comprising: a receiver configured to receive Reference Signal (RS) configuration information for phase estimation on self-interference from a base station; a transmitter configured to transmit an RS based on the RS configuration information based on that the user equipment operates in an inter-panel Space Division Duplex (SDD) or Full Duplex Radio (FDR) mode with a distributed antenna structure; and a processor configured to perform phase estimation on inter-panel self-interference based on the RS.
 14. The user equipment of claim 13, wherein based on that the user equipment operates in the inter-panel SDD or FDR mode with the distributed antenna structure and a scheduled MCS level of the user equipment is smaller than an MCS level threshold related to the RS or a scheduled bandwidth is smaller than a predefined bandwidth, the transmitter is controlled to transmit the RS for the phase estimation on the inter-panel self-interference.
 15. The user equipment of claim 13, wherein the transmitter is configured to transmit a request message for transmitting the RS to the base station, wherein the receiver is configured to receive control information indicating that the RS configuration information is valid from the base station, and wherein the transmitter is configured to transmit the RS based on the RS configuration information and the control information.
 16. The user equipment of claim 13, wherein the user equipment is capable of communicating with at least one of another user equipment, a user equipment related to an autonomous driving vehicle, a base station or a network. 